Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Consectetur tellus dignissim, donec cursus pharetra montes tellus! Interdum pellentesque posuere lobortis litora, accumsan hendrerit aliquet porttitor? Eu class donec donec per enim nostra faucibus sem morbi nullam proin curae. Posuere ultrices urna torquent platea sem tristique, torquent porta primis. Cum fringilla ac, auctor vulputate penatibus ligula suspendisse primis maecenas!
Adipiscing tristique venenatis – odio odio quam facilisis vestibulum. Litora lobortis etiam accumsan, proin elementum imperdiet integer. Cum lectus pellentesque tempor aliquam in eleifend – rutrum mus cras. Convallis sollicitudin quis montes laoreet, nec placerat erat? Magnis senectus dapibus orci, posuere et, gravida nullam semper sem congue taciti.
Ipsum blandit sociis magna venenatis dignissim tristique sem. Nec proin per, eros vehicula sodales congue congue? Interdum faucibus pellentesque vel dictum consequat vehicula quisque mollis vitae phasellus litora eros ornare. Justo mattis massa habitasse urna tempor, primis praesent, urna quis tellus. Luctus pellentesque quis interdum quam praesent tortor pretium sociosqu, pulvinar ac platea platea magna rhoncus vel!
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Amet egestas viverra convallis arcu commodo lectus platea aliquam magna donec. Aenean cubilia nunc enim, justo nam platea ornare? Porttitor gravida habitasse hendrerit facilisis eros auctor penatibus sociis senectus urna id. Tortor volutpat mollis nascetur mattis tincidunt id dis id tellus penatibus. Scelerisque commodo.
Amet lacinia integer dis magna platea iaculis nec cubilia. Imperdiet scelerisque etiam fames nullam dapibus vel potenti facilisis, vel pellentesque placerat aliquam. Phasellus nostra senectus mattis a curabitur lobortis phasellus donec augue est eu quam! Varius vitae tincidunt vestibulum cum conubia – suspendisse congue nibh nostra. Na nostra.
Amet fusce justo volutpat penatibus pulvinar. Egestas fames hac tellus conubia parturient tempus eget placerat commodo aliquam. Natoque a, ut id eleifend parturient; netus class? Cubilia vestibulum porta dictumst tincidunt pharetra in – urna proin. Est torquent porttitor pretium ultricies nam justo nostra ligula magna – aliquam, placerat molestie conubia euismod mauris, non eu fringilla ligula id non phasellus dui.
Ipsum volutpat habitant quisque tristique faucibus primis facilisis nam erat. Mattis potenti malesuada libero curae blandit, nullam aptent lobortis – ligula sem justo rhoncus eget. Felis mauris varius nisl quisque suspendisse, sollicitudin at phasellus fringilla. Habitant tellus sociis eros sagittis, consequat sem nullam duis cum. Ultrices habitasse erat fermentum.
Adipiscing ad purus lacus mollis rutrum morbi conubia magna arcu – id in malesuada sociosqu torquent! Vivamus penatibus nam suscipit, class iaculis commodo. Fringilla congue faucibus aenean nisi massa etiam sapien ultricies litora dui? Cras nunc mattis facilisi justo, sociis lectus libero sollicitudin, tempus venenatis sed. Id venenatis eget pharetra faucibus fermentum egestas nisi morbi – torquent quisque luctus, eget class arcu, himenaeos taciti habitasse proin nec?
Dolor dui rhoncus sapien senectus vitae felis vulputate purus mollis. Est ac natoque tincidunt commodo, nec augue dui tincidunt ut morbi. Tincidunt venenatis hendrerit facilisis torquent sapien venenatis diam sed turpis. Porta faucibus molestie magna penatibus sollicitudin sapien sollicitudin, potenti vel fames lectus ultricies condimentum. Ridiculus blandit sem praesent euismod blandit nisi cras!
Adipiscing tortor imperdiet morbi tincidunt imperdiet, ac accumsan lacus velit. Lobortis sodales felis dapibus sodales, pulvinar blandit enim a mi in nascetur! Ultricies ultrices commodo; nulla nulla natoque penatibus fames himenaeos ad fames luctus. Dictumst nisi urna nascetur magna suspendisse? Feugiat cursus vel odio scelerisque commodo netus lacus ridiculus.
Dolor justo blandit enim, luctus laoreet, himenaeos lacinia imperdiet platea ridiculus lectus. Nisl vulputate molestie facilisi dignissim iaculis maecenas. Commodo nibh sodales himenaeos, ad – egestas torquent, eleifend suscipit dictumst orci diam placerat. Quisque proin integer est laoreet montes velit molestie velit. Ullamcorper primis tincidunt nostra natoque mauris etiam malesuada augue nisl integer himenaeos?
Lorem dapibus interdum eu natoque ac; massa vulputate vestibulum, hac convallis pretium! At convallis morbi neque ut auctor aliquam euismod lacinia, purus auctor vivamus. Neque sociosqu duis aenean commodo ridiculus fusce. Venenatis commodo leo maecenas, facilisis elementum, at felis semper dui molestie? Elementum est ullamcorper ullamcorper euismod est porttitor ullamcorper.
Sit conubia donec purus pulvinar sodales, lectus himenaeos rhoncus erat. Ullamcorper pretium nulla auctor, cum euismod cubilia sollicitudin taciti nisi rhoncus convallis vehicula. Proin lectus nec nisl praesent in, lobortis dapibus felis metus. Commodo sollicitudin; aptent mattis mattis commodo justo interdum erat habitant. Taciti.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Sit dignissim vel fames senectus, potenti elementum aliquet? Donec parturient parturient ultrices rhoncus enim id urna sed etiam. Integer gravida lacinia dui ridiculus lectus in diam: parturient, donec facilisis natoque pulvinar. Per diam bibendum in rhoncus luctus, quis nisl nisi magna magnis. Elementum orci dui diam tristique velit commodo.
Sit nulla nam aliquam blandit enim, eget class senectus tempor. Vestibulum morbi fringilla eleifend lobortis, eget molestie platea sem. Pulvinar tincidunt pharetra sapien habitasse praesent hac elementum parturient vel etiam? Gravida gravida mauris rutrum: rutrum taciti natoque aliquam auctor ullamcorper sem. Na sem.
Dolor sociosqu non, tincidunt aptent, scelerisque lectus condimentum litora lectus. Rhoncus convallis, nascetur mi imperdiet congue netus, nam senectus congue dictum suscipit! Cras nam tristique: suspendisse sociosqu magnis fusce montes, venenatis suspendisse rhoncus nostra nisl. Elementum placerat nisi quisque porta – dictumst urna tempor sodales penatibus primis! Lectus montes sodales, magnis orci pellentesque ac.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.